Collapsible screw-tap



(No Model.)

4 J. M. JOHNSON,

GOLLAPSIBLE SURE-W TAP.

No. 297,519. Patented Apr. 22,1884.

N. PETERS. Pholo-lillm m lm. Washlllg c.

UNITED STATES PATENT I OFFICE.

JAMES M. JOHNSON, OF CLEVELAND, OHIO.

COLLAPSIBLE SCREW-TAP.

SPECIFICATION forming part of Letters Patent No. 297,519, dated April 22, 1884.

' I Application filed August 8, 1883. (No model.)

To all whom it may concern.-

Be it known that I, JAMES M. J oHNsoN,'of Cleveland, in the county of Ouyahoga and State of Ohio, have invented certain new and useful Improvements in Collapsible Screw- Taps, of which the following is a specification.

In the accompanying drawings, Figure l is a side elevation. Fig. 2 is a longitudinal sectionT Fig. 3 is an end view. Fig. 4 is a crosssection in line as w on Fig. 2.

The object of my invention is to furnish a device by which to collapse the cutting-dies in a screw-thread-cutting tap, so that when the screw-thread has been cut the dies may be closed inward to enable the tap to be Withdrawn without the necessityof a reverse rotary movement for that purpose.

A is a hollow mandrel, providedat the cutting end with slots or seats for the cuttingdies B B.

C is a tapering rotary core, fitting in the hollow of the said mandrel. Its forward end is provided with'grooves 0, into which the dies drop when the core is turned for that purpose. Upon the large part of the mandrel is placed a rotating sleeve, D, and upon this is placed a second sleeve, E, secured to the sleeve D by a set-screw, 6. Through the first sleeve, D, is made a hole, (1, through which is put a lever, F, which is secured to the core 0 by a sliding nut, f, the core having a slot through which the lever passes for the purpose of enabling the core to be adjusted lengthwise by the screw n. In the mandrel is made a radial slot, a,

for the lever to play in when turning the core. The front edge of the sleeve Ehas incline projections t i, which serve to force the dies inward when it and the core are turned by the lever. Inthe sides of the mandrel, at the forward end, and located between the dies, are 0 D around on the mandrel, which brings the grooves c in the core under the dies, into which they are forced by the inclinesz' i of the sleeve E. The tap is then readily removed fromthe work.

Having described my invention, I claim- 1. In combination with the cutting-dies constructed in two parts, the strip h, for adjusting said parts outwardly, as and for the purpose set forth.

2. The tapering core 0, having the grooves c in the forward end, and the slot f, substantially as described.

3. The sliding nut f, in combination with lever F and core 0, as and for the purpose specified.

4.. In combination withthe tapering core 0, having slot f, the lever F, nut f, mandrel A, and the adjusting-screw n in the rear end of said hollow mandrel, for adjusting and securing the core in place, substantially as described.

JAMES M. JOHNSON.

Witnesses:

GEO. B. TIBBITTs, E, W. LAIRD. 

